The present invention relates generally to intraocular lenses, and more particularly to intraocular lenses whose focusing performance can be adjusted externally after implantation in an individual""s eye, without a need for any invasive procedure.
The lens and the cornea of the human eye provide a combined refractive power of approximately 60 diopters (D), with the cornea providing about 40 D of the power and the lens providing about 20 D of the refractive power. Certain diseases of the eye, such as cataracts, cause the lens to become progressively opaque. The opacity typically worsens over time, and can ultimately result in blindness. It is typically necessary to surgically remove the opaque lens to allow an unobstructed transmission of light to the retina. The removal of the lens, however, deprives the eye from the substantial refractive power that the lens provides.
When the natural lens is removed from the eye, an intraocular lens (IOL) can be implanted in the eye to assist the eye in focusing light onto the retina. Intraocular lenses typically provide one or more fixed focusing performances. Typically, the needed refractive correction(s) is (are) determined before implantation of the IOL in the eye. Such pre-operative predictions of the needed corrective power are sometimes not sufficiently accurate. Furthermore, once implanted, an IOL can shift position within the eye, thereby causing a loss of focus. Hence, an individual having an implanted IOL may require additional corrective devices, such as glasses, to acquire the desired visual acuity.
Accordingly, it is object of the present invention to provide an intraocular lens whose focusing performance can be modified in situ.
It is another object of the invention to provide an intraocular lens whose focusing performance can be externally modified after implantation in the eye.
It is yet another object of the invention to provide an intraocular lens whose focusing performance can be adjusted over a selected range.
The present invention attains the above and other objects by providing an intraocular lens whose focusing performance can be adjusted over a selected range after implantation in a patient""s eye without a need for an invasive procedure. In particular, the focusing performance of an IOL according to the invention can be modified by application of energy, such as magnetic or electric energy, supplied from an external source to the IOL. An intraocular lens according to the teachings of the invention includes an optical chamber deformable under influence of pressure from a fluid. The IOL further includes a reservoir, in fluid communication with the optical chamber, for storing an optical fluid. A valve regulates the fluid communication between the reservoir and the optical chamber.
As used herein, the term xe2x80x9copticxe2x80x9d or xe2x80x9coptical bodyxe2x80x9d is intended to encompass the component(s) within the intraocular lens of the present invention that cumulatively enable the intraocular lens to focus the light. The optic can include an optical chamber and optical fluid within such chamber, as well as one or more physical lens structures, if desired. The term xe2x80x9cintraocular lensxe2x80x9d, as used herein, encompasses all of the above described optical elements and other structures such as haptics useful for attaching the IOL to the eye as well as other structures elaborated below.
The IOL can further include a pump capable of being actuated by an energy source external to the eye to cause a flow of a selected volume of the optical fluid between the reservoir and the optical chamber. A flow of the optical fluid into and/or out of the optical chamber selectively varies an amount of fluid in the optical chamber. The change in the amount of fluid in optical chamber can vary a pressure exerted on the flexible portion(s) of the optical chamber to cause a change in radius of curvature of the flexible portion(s) and/or vary a distance between optical surfaces of the optical chamber. Such changes in the optical chamber can lead to a change in the focusing performance of the IOL.
The external energy source can include, but is not limited to, a magnetic field generator, an electric field generator, or a source of photons, such as a laser. In one preferred embodiment, an oscillatory magnetic field is employed for actuating the pump. In another embodiment, a rotating magnetic field is employed for activating the pump.
In general, the index of refraction of the optical fluid useful in the present invention can have any value. In most implementations, however, the index of refraction of the optical fluid is preferably selected to be greater than approximately 1.337. One preferred embodiment of the invention employs silicone with an index of refraction of about 1.4 as the optical fluid.
In many implementations, the IOL can include an optical body having two optical elements, at least one of which has a flexible convex region. These elements form an optical chamber therebetween. In such an embodiment, pumping a volume of the optical fluid into the chamber increases the hydrostatic pressure within the optical chamber and hence causes a decrease in the radius of curvature of the flexible region of the chamber. Such a decrease in the radius of curvature, in combination with the focusing performance of the fluid, leads to an increase in the focusing performance of the intraocular lens.
The IOL device can also include one or more haptics to allow fixation of the lens within the eye. The haptics can also include the reservoir of fluid for use in modifying the shape of the optical chamber.
One embodiment of the present invention provides an intraocular lens that employs a gear-pump. Such an intraocular lens includes an optical body having at least an optical chamber with at least a flexible region deformable in response to an applied pressure. A reservoir, which is in fluid communication with the optical chamber through a valve positioned between the reservoir and the optical chamber, stores a selected volume of an optical fluid. The gear pump is configured to be actuated by an energy source positioned external to the eye to cause the optical fluid to move, through the valve, between the optical chamber and the reservoir.
The gear pump can include a pair of inter-locking gears formed, for example, of silicone rubber. At least one of the gears is selected to be magnetically rotatable, for example, by implanting a permanent magnet in the silicone rubber. An external magnetic field generator can be utilized to apply a rotating magnetic field to the magnetic gear to cause a rotation thereof. The rotation of the magnetic gear in turn causes a rotation of the other gear, i.e., the gear engaged with the magnetic gear, in an opposed direction. The combined rotation of the gears controls the flow of the optical fluid between the reservoir and the optical chamber of the lens.
Another preferred embodiment of the invention employs a peristaltic pump for providing fluid communication between an optical chamber and a reservoir of an optical fluid. The peristaltic pump can also include a valve for regulating the flow of the optical fluid between the reservoir and the optical chamber. A magnetic field, such as an external rotating magnetic field, actuates the peristaltic pump according to the invention by inducing a propagating deformation, e.g., constriction, therein, which causes a flow of the optical fluid between the reservoir and the optical chamber. Thus, by actuating the pump, the clinician (or the subject) can calibrate or tune the focusing performance of the IOL to a desired value.
A peristaltic pump according to the teachings of the invention can have a tubular structure that is formed, for example, of a resilient material such as silicone rubber, or another polymeric elastomer. A plurality of magnetic particles, such as ferrite, magnetite, nickel cobalt, neodymium, boron, samarium, iron or compounds or alloys of such materials, are distributed within the wall of the tubular structure such that a rotating magnetic field can be applied to the tubular structure to induce a propagating constriction within the tubular structure. The propagating constriction causes the optical fluid within the tubular structure to flow from one end of the structure to the other, thereby inducing the fluid flow between the reservoir and the optical chamber.
Another embodiment of an intraocular lens according to the teachings of the present invention utilizes a diaphragm pump to transfer an optical fluid between an optical chamber, formed in the optical body, and a reservoir for storing the optical fluid. The diaphragm pump can be actuated by an energy source positioned external to the eye. For example, the diaphragm pump can be magnetically and/or electrically actuated.
The diaphragm pump can include a housing having an inlet opening and outlet opening, and further can include a flexible diaphragm disposed in mechanical communication with the housing. The diaphragm can be formed of a material such as Silicon (Si), Titanium, Stainless Steel, and can be selected to have at least one resonant vibrational frequency. Alternatively, the diaphragm can be formed of elastomeric materials such as poly(dimethylsiloxane) (PDMS). Application of an oscillatory magnetic field having an oscillation frequency which is substantially similar to the resonant vibrational frequency of the diaphragm induces a large amplitude oscillation in the diaphragm, and thereby causes a flow of the fluid between the inlet and the outlet openings.
In yet another embodiment of the invention, the intraocular lens can employ a peristaltic micro-pump utilizing a ferro-fluid material. The IOL can again include an optical body having a base portion and a cover portion that form an optical chamber therebetween. At least one of the cover or the base portions has a flexible region that is deformable in response to an applied pressure. The base portion includes a reservoir for storing an optical fluid, and further has a channel for providing fluid communication between the reservoir and the optical chamber by providing a flow path for the optical fluid. The cover portion has a channel for storing a ferro-fluid material. The channels of the base portion and the cover portion are preferably substantially aligned. A flexible membrane disposed between the channels of the base and the cover portions isolates the ferro-fluid from the optical fluid. The ferro-fluid material can be externally actuated, for example by an external magnetic energy source, to provide a propagating pressure on the flexible membrane. The propagating pressure in turn produces a propagating deformation of the membrane to cause transfer of a selected volume of the optical fluid between the reservoir and the optical chamber. Ferro-fluid materials suitable for use in the intraocular lens of the invention can include oil-based ferrofluids such as silicone oil or petroleum distillate suspension of nanoparticles of magnetite (Fe3O4), Iron, Cobalt, Iron nitride (Fe3N) in which the nanoparticles are typically coated with an ultra-thin layer of surfactant to keep the particles suspended.
In another aspect, the invention provides an intraocular lens that has an optical body having at least an optical chamber and at least a flexible region that is deformable under influence of a fluid. Further, the IOL includes a reservoir for storing a selected volume of an optical fluid. The reservoir is in fluid communication with the optical chamber through a valve which regulates the flow of the optical fluid between the reservoir and the optical chamber. The IOL includes at least one magnet positioned between the reservoir and the optical chamber and pivoted about a rotation axis at an end thereof. A magnetic field supplied by an external magnetic energy source can actuate the magnet to cause it to rotate about its pivot point, thereby forcing the flow of the fluid in a selected direction, for example, from the reservoir to the optical chamber. The IOL can also include a second magnet positioned along a vector directed from one pole of the first magnet to its other pole such that the opposite poles of the first and second magnets are proximate of each other. The magnets can be actuated by an external magnetic source to rotate in opposite directions, albeit about the same rotational axis, to cause a flow of the optical fluid through the valve between the reservoir and the optical chamber.
Another intraocular lens according to the teachings of the invention employs a micro-pump that utilizes at least one ball formed of a magnetic material. Such magnetic material is preferably selected to be soft and can include, for example, silicon steel alloys (2.5%-6% Si and Fe in balance) or iron-cobalt alloys such as, Fexe2x80x94Coxe2x80x94Vxe2x80x94Nb alloys, e.g., Carpenter Hiperco alloy. Such an IOL includes an optical body having a base portion and a cover portion that form an optical chamber therebetween. The base portion has at least a flexible region and further has a reservoir which is in fluid communication with the optical chamber. Further, the cover portion has a channel that includes a surface having at least a flexible portion in contact with at least a portion of the fluid. A valve positioned between the reservoir and the optical chamber regulates the fluid communication between the reservoir and the optical chamber. The ball is positioned in the channel of the cover portion and is actuated by an external magnetic source to move within the channel such that it produces a deformation of the flexible membrane. This deformation, produced in the vicinity of the ball, in turn causes a flow of the fluid through the channel between the reservoir and the optical chamber.
Although the invention is described in terms of discrete xe2x80x9cbasexe2x80x9d and xe2x80x9ccoverxe2x80x9d portions, it should be clear that an IOL of the invention can be constructed as a unitary structure having two surfaces corresponding to the base and cover portions described above. Moreover, even when two components are formed in manufacturing of the IOL, the construction process can be such that the xe2x80x9cbasexe2x80x9d and xe2x80x9ccoverxe2x80x9d components are completely fused so as to form an essentially unitary structure.
A further embodiment of an IOL of the invention can employ the Faraday effect to actuate a piezo-electric element which in turn actuates a diaphragm pump. In particular, the IOL includes an optical body having an optical chamber and at least a flexible region that is deformable in response to an applied pressure. The optical body further includes a reservoir for storing an optical fluid. The piezo-electric element can be actuated by energy, such as a time-varying magnetic flux, provided by an external source, to cause the diaphragm pump to transfer a selected volume of the optical fluid between the reservoir and the optical chamber.
The piezo-electrically driven diaphragm pump can include a housing having inlet and outlet openings (which can be one-way valves), a flexible membrane that is in mechanical communication with the housing, and a piezo-electric element in contact with the diaphragm. A periodic modulation of the stress in the piezo-electric element, induced, for example, by an oscillatory flux, can result in a mechanical oscillation of the diaphragm. Such an oscillation of the diaphragm forces a fluid within the diaphragm housing to flow between the inlet and the outlet openings of the diaphragm pump.
An intraocular lens according to another aspect of the invention can include a vapor-operated pump. The vapor-operated pump can include housing having a reservoir of a selected volume of a fluid, e.g., water, in contact with a flexible membrane. A resistive element, such as a resistor, energized by an external energy source can be employed to periodically turn the fluid into vapor, thereby providing a periodic pressure change against the flexible membrane. This periodic pressure change in turn causes a periodic deflection of the diaphragm that provides a pumping action for transferring fluid through the housing of the pump between an input port and an output port (which can be one-way valves).
In another aspect of the invention, a pump for transferring the optical fluid between the reservoir and the optical chamber employs reverse electrophoresis.